#include <iostream>

using namespace std;

const int N = 1010;

int f[N][N];
int main()
{
	string s; cin >> s;
	int n = s.size();
	s = " " + s;
	for(int len = 2; len <= n; len++)
	{
		for(int i = 0; i + len - 1 <= n; i++)
		{
			int j = len + i - 1;
			if(s[i] == s[j]) f[i][j] = f[i + 1][j - 1];
			else 
			{
				f[i][j] = min(f[i + 1][j] + 1, f[i][j - 1] + 1);
			}
		}
	}
	cout << f[1][n] << endl;
	return 0;
}
